Notes: Today you get two words for the price of one, though you wouldn't think so, since the two are spelled and pronounced identically. However, they are used in radically different ways; one is a noun, the other, a verb. Below we will see that they were not always so different.

In Play: The verbal sense of this good word is quite positive, "I plighted you my word that I will not embarrass you on the dance floor tonight and I won't." If you are looking for an inventive way to propose marriage, where better to look than the past? "I plight my troth (fidelity) to you forever, Adelaide; will you do the same?" Although the noun plight is more often used in negative sense, "The plight of Iraq has been alleviated by the removal of Saddam Hussein from power", it can also refer to the health of animals: "My cow is in good plight, so we needn't worry any more about milk."
Word History: The verb plight comes from Old English plihtan "to endanger, put at risk" from pliht "danger, risk"—some of which meaning still lurks beneath the surface of the phrase "to plight one's troth". It goes back to the PIE root *dlegh- "to be occupied", which also surfaced in English as play and pledge. The story of the change from [d] > [p] is a story of 'dissimilation', changing the [d] to another sound because it was too much like neighboring [l]. As we go back this far, we see that the two English words emerged from the same Old Germanic word, for origin of the noun plight is also Old English pliht "danger, risk". (We plight our gratitude today to Tim Ward for suggesting this interesting word split, keeping us from facing the plight of no good word for today.)

The Swedish cognate is «plikt», most commonly used in the sense of «duty» (the late king's motto was «Plikten framför allt»). Interestingly enough, another word, written and pronounced exactly the same and with cognates in other early Germanic tongues (including Old English), refers to various types of decks in small boats....

They obviously are too dissimilar to have any genetic relationship, but it would perhaps be interesting to look at pl- words to see if there is some common feature. Compare sloppy words like slow and sloth, the snotty and snide ones, the blowing, bloating and flowering words of so many different languages...